Processing of materials



Oct. 23, 1945. E. L. WIEGAND PROCESSING OF MATERIALS Original Filed Dec. 7, 1939 7 Sheets-Sheet l dw'm L. Wm

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Oct. 23, 1945. E. L. WIEGAND PROCESSING OF MATERIALS Original Filed Dec. '7, 1939 7 Sheets-Shut '7 IN v ENTO R BY M, M ATTDRNLYS Edwin vL.. Wiagouad I and the grinding or materials.

Patented Oct. 23., 1945 NI ED STATES PATENT omen a 2,331.54:

PROCESSING OF MATERIALS Edwin L. Wlegand, Pittsburgh, Pa., raim to Orefraction Incorporated, Pittsburgh, Pa., a corporation of Pennsylvania Original application December. I,- 1939, Serial No.

308,002. Divided and this applicationOc ber 24, 1940, Serial No. 362,563

31 Claims.

v.lilly invention relates to the processing of materials, and more particularly, the processing materiali from an unground state to a ground product or to several separated ground products, with respect to the grinding of materials, the invention involves the projection of a stream of fluid and material particles moving at high velocity against an anvil or against a counter-stream of particles. The principal obiects 'oi the invention are the improvement or methods and apparatuses for carrying out such processing of materials, and the provision of new and improved materials. This application is a division of my application Serial Number 308,002, filed December 7, 1939.

In the drawings accompanying this specification and forming a part of this application, there are shown, for purposes of illustration, several embodiments of apparatus embodying .the invention, and in these drawings: Figure 1 is a more or less diagrammatic view of the relation between material conveying means, grinding means, and separating means, as these means may be utilized in one embodiment of my invention, v

Figure 2 is a more or less diagrammatic view, particularly showing the fluid connections between parts of the apparatus,

Figure 3 is a detail elevational view of the grinder caseand one connected single-stage material-proiecting gun,

Figure 4 is an enlarged longitudinal sectional view of a portion of the gun shown in Figure ,3,

Figure 5 is a sectional view corresponding to the line 6-li of Figure 4,

Figurefi is an enlarged sectional view corresponding generally to the line 6-6 of Figure 4,

Figure 7 is an enlarged fragmentary sectional view showing certain parts, adapted to provide an air jet, of a gun such as shown in Figures 4 and 6,

Figure 8 is an enlarged sectional view through the grinder case,

Figure 9 is an enlarged vertical sectional view corresponding generally to the line 9-9 0! Figure 8, t

Figure 10 is an enlarged horizontal sectional view corresponding generally to the line "-40 of Figure 9, Figures 11, 12, and 13 are sectional views respectively showing diflerent gun arrangements,

1 a Figure 14 is a broken sectional view with parts in elevationshowing a two-stage gun,

Figure 15 is a broken elevation view showing a three-stage gun,

Figure 16 is a sectional view showing a multistage gun arrangement,

Figure 1'! is an enlarged sectional view 01 a portion of Figure 16,

5 Figure 18 is a sectional view corresponding to the line l8-l6'oi' Figure 17,

' Figure 19 is a broken elevational view of a gun construction comprising adjustable and fixed stages,

10' Figure 20 is a broken elevational view of an embodiment of a gun construction comprising fixed stages only, and

Figure 21 is a broken sectional view oi-another gun arrangement comprising plural opposed guns.

15 The term materiaris used herein to include any substance of a divided nature, as distinguishedirom relatively large blocks of substances. The term grinding isused herein in its broader aspects as meaning reduction in size, in any way,

20 oi the material being treated, and in its more specific aspects, such grinding as occurs when-material is subjected to impact. Example of material which may be-ground by an apparatus embodying my invention are such materials as zir- 25 con, rutile, quartz, ieldspan'fluorspar, marble,

glass, enameling frit, hard metals, artificial or other abrasives, industrial diamonds'and many others either of similar or diflerent characteristics. My invention is particularly adapted to reduce hard, tough, and abrasive materials, includ- Also it is int; ores having these characteristics. particularly adapted to grind material to ultraflne sizes, such as for example -200 mesh to micronsizes. Preferably the material to be ground should not be larger than 16 to 18 mesh size,although it is possible to accommodate larger sizes. In general the size to be commenced with may be any desirable size which cannot be better or more economically crushed otherwise, but the size 40 of the material to be ground is related to gun size,

and therefore also to the capacity oi the apparatus. However, the capacity of apparatus embodying my invention is very great in relation to the gun bore area, as will fully appear herein- 45, after.

Referring to the schematic arrangement shown in Figure 1, the embodiment of the invention there illustrated comprises a container adapted to contain material to be ground, and hereafter 50 referred to as the new-materials container. The

new-materials container 50 may be formed with an outlet spout II discharging into a funnel 52 carried by the receiving end 53 of an elevating device 54, such as the bucket elevator here shown.

55 A suitable slide valve 55 is interposed in the outof the motor 66 of the,

' let spout 6| to regulate the flow of material from the new-materials container 66 to the receiving end '66 of the elevator 64. The elevator 64 may be driven by means of an may also have a signal device, such a the electric light 61, to indicate when the elevator 64 is operating. I The discharge end 66 of the elevator 64 discharges into a conduit 66 leading to a blending and metering hopper 66, having high and low limit controls 6| and 62, so as to controloperation elevator 64, the connections being such that the motor 66 of the elevator 64 is automatically started when the level of the material falls enough to actuate the low level device 62, and the motor .66 is automatically stopped when the material rises enough to actuate the high level device 6|. The details of the blending hopper 66 and the controls therefor are described in my aforesaid application and, as far as the subject matter of the present application is concerned, these details need not be set forth herein.

Positioned alongside or the second elevator 63, having its inlet end 64 receiving material from the lower end of the hopper 66, as by means of a conduit 65, a suitable receptacle 66 is a slide .valve 66 being so interposed as to control the amount of material flowing from the hopper 66." The elevator 63 is driven by an electric motor 61, and may have a signaling 'device, such as the electric light 66, to indicate when the motor 61 is running. The discharge end 66 of the elevator 66 leads to the inlet of a solids valve, I6

electric motor 66, and

Means, shownwin Figure 2, is provided for admitting .air under pressure to the upper and lower is in'the lower grinder case 66, the ground the outlet of which communicates withthe in terior of a charge metering and hoist tank II. The hoist tank 'II has high and low level .dev'ices I2 and I6 respectively, so related to other parts (as described in my aforesaid application) as to permit the motor 67 to operate when the material is belowthe low level device 13, and to interrupt the circuit of the motor 61 when the material reaches the high level device 12.

A fluid under pressure, in the present instance, air, may be admitted to the hoist tank (I through a conduit 14, and such air may be released from the hoist tank II through either the conduit I4 or a blow-oil conduit I5. With material in the hoist tank II, and air under pressure supplied to the hoist tank 1| through the air conduit I4, the material in the hoist tank 1| is forced to move into the lower end of a tube 2| 6 suitably connected at its upper end to and in communication with a conduit 16, the material continuing through the tube 2| 6, through the conduit 16 to a connection conduit 11 between an air strainer tank 16 and an upper material feed tank 16, a valve 66 being interposed in the connection conduit TI to permit admission of material to the upper tank I6 and to enable the tank to be placed under fluid. pressure. Assuming the valve 66 to be in open position, the material which passes through the conduit I6 is delivered to the connection conduit 11, the air used for hoisting purposes being strained by and vented from the strainer tank 16, the upper feed tank I6. The conduit 16 is preftanks 16 and 6|, as will more fully appear.

Assuming that the valve 66 is closed and the valve is open, and assuming also that material tank 6|, and that this tank is under air pressure, the material from thetank 6| will be forced through the outlet conduit 64, and through'a hose conduit 66 of a gun 66, and through this gun 66 to the material passing through a conduit 66 t0 a first separating device 6| of the cyclone type. The surfaces in the device 6| which might be subject to abrasive wear may be suitably lined with rubber. material in the first separating device 6| may gravitate through a tube 6' against a check valve 62, this valve being so constructed and arranged that a predetermined head of material is built up and maintained at the dischargeend of the separating device-6|, material being permitted to 9ggavitate past the check valve, into the conduit charge end of the separating device. Any suitable check valve may be used and instances are described in my aforesaid application. The material then continues through the conduit 63 to a funnel 64, and from the funnel 64 to ascreen chamber 66 of a screening device 66. The screening device 66 may be of the vibratin type. having a screen 61 over which the material is shucked, the screen having a certain predetermined mesh size, as for example 200 mesh.

The material which passes through the screen 61 falls into a hopper 66, the outlet of the hopper 66 having a bagging device 66, to which a bag I 66 is attached. the bag J66 receiving such ma terial for shipment if desired. For convenience. the bag I66 may be disposed on a platform |6| of a scale I62, delivered to the bag is delivered to the bag- That material which does not pass through the screen 61 is discharged from the screen chamber 65 through a conduit I66, and back to the mixing hopper 66. Additional material, from the new materials contain 6 er.56, may be added to the. hopper 66 by means of the elevator 54, the high level device 6| limiting the amount of new material delivered to the hopper 66. In this manner the material removed from the system is automatically replaced with new material from the new materials conflow rate. such rate being determined by the rate at which finished material is removed from the system. v

Additional separating means is provided for additionally separating that material which does I desired in' two diametrically disposed tangential branches 6a and H612. Slide valves III and to the breach 6'! The heavier,

as further material accumulates in the dis-- so that the amount of material I66 may be weighed as it one branch I61 leading dered settling.

duit m and 2,887,348 I u: are respectively interposed in the branch conduits I31 and I33, these valves being independently adjustable so as to regulate the amount of air discharged by the blowers through the respective branch, for a purpose to appear.

The upper discharge outlet of the separating device 3 I is connected to the inlet of the blower chamber I33, and in this instance certain devices are interposed in this connection. Extending from the upper discharge outlet of the first separating device 3| is a separating column, H3, or any suitable cross-sectional form, area, and length, which extends vertically and to a conduit H3 which is tangentially connected to the upper end of a second air separating device H3. Desirably the separating column H3 is enlarged with respect to the conduit H3, and may taper toward its lower end to cause hin- The'de'vice H3 may be of the cyclone type, comprising a chamber having an upper cylindrical portion H1 and a downwardly tapering conical portion H3. A bagging device H3 is connected to thelower end of the conical portion H3, and has attached thereto a bag for receiving material gravitating downwardly of; the conical portion H3. The upper end of the second separating device H3 is formed with a housing I2I communicating with the interior of the .device H3. The housing I2I communicates by means of a conduit I22 with a dust collector or separator I23, which may be of any suitable type. The rator I23 has attached thereto a bagging device. I23, and the air outlet of the dust separator- I23 is connected by a conduit of the fan chamber I33.

Assuming that the motor I33 is operating, and that the valve III is at least partially open, that ground material. along with air used in grinding it, is being delivered throughthe conduit 93 to the first terial which under the air conditions prevailing in the separating system is not heavy enough to gravitate at once from the separating device 3|, will be picked up by the stream of air in the column H3. Some of this material will con- ,I23 to the'inlet tinue to be carriedby that stream to the top of the column H3 and through the conduit H3 is connected lower end of the dust sepa-' and separating device 9|, the mapressure) can be separating device whereby material readily back pressure 10 in the grinder case 33 pressure, 81$ may be -to the position made to. exist in the first sepa rating device 3|. Usually the valve H2 is partially or completely tially or completely open, so that anunder-pressure or partial vacuum exists within the: first 3| and in the column H3, asses from the grinder case" to the first separating. device 3i, and no is created in the conduit 33 leading from the grinder case 33. Alsapsually the valves III and II2 are adjusted toeifect substantially zero (atmospheric) pressure in the grinder case 83, thereby to avoid back pressure that might interfere with the operation of the grinder gun. However, it will be apparent that the pressure conditions in the grinder case and in the separating system can be regulated by adjustment of the slide valves I H and conditions. Furthermore, the velocity of the upwardly moving stream of air in the separating column H3 may be'adjusted to a most suitable velocity so that column H3 will be optimum.

Since a certain head of material is maintalned withinthe tube 3'" by the valve 32, air communication between the conduits 33 and the interior of the first separating device 3| is prevented. Thus the pressure condition within the 'device3I, either greater or less than atmospheric since the check valve 32, either open or closed, substantially prevents fiow of air through the tube 31 I The first separating device 3| may be moved from the position shown in full lines in Figure 1 shown in dotted lines, wherein its lower end no longer communicates with the conduit 33, but instead'communlcates with a conduit I33 leading to a tankv I33, hereinafter referred to as a by-pass tank. The lower end of the tank I33 carries a bagging device I31, to which a bag I33 may be attached, and a check valve I33 is. interposed in the conduit I33, the

to the upper end of the second separating device H3, and will end because of the be caused to swirl in this upper tangential connection of the conduit H3. The heavier materials in the second separating device H3 will gravitate downwardly through the conical portion H3, and will be delivered to the bag I23 through thebaggingdevice I I3. The upwardly by the lighter material will be carried air stream through the housing I2I and the conduit I22, to the dust collector device 3| does not continue with the upwardly.

moving stream ofair into the conduit H3, but gravitates back through thestream into the separating device SI and finally reaches the lower or discharge end of the separating device 3|,

and thus the separating action of the system is improved.

Depending upon the setting of the slide valves HI and I I2, either an under-pressure or an overpressure condition .(with respect to atmospheric check valve I33 being provided for the same purpose as the check valve 92. In this position of the device 3| the ground material, excepting only a controllable amount and'size of very fine material, instead of going to the screen chamber 33, passes directly to the by-pass tank I33. The conduit H3 in this position may still be connected to the conduit H3. The by-pass tank connection is particularly useful when it is desired to make an unscreened ground aggregate, with only a minimum of extreme fines removed.

The fluid pressure system is particularly shown in Figure 2,- and in this embodiment uses air as the fluid, although be used. The system comprises an air compressor I33, a conduit I33 leading from the air compressor I33 to an air storage tank I31, and a three-way valve I33 interposed in the conduit and the storage any desired pressure is built up: in the tank I31.

closed, and the valve III par- I I2 to obtain any desired pressure the separating function of the 1 desired, will not be changed, i

any other suitable fluid may from the storage tank I 62 topassing from the conduit The valve I46 isthenlturned to establish co munication between established communication between the waste air tank I49 and a conduit I52, for a purpose hereinafter explained. A manual control valve I65 may also be interposed in the conduit I46 for controlling the flow of air through the conduit I46, and a pressure indicator I54 the valve connected to the storage tank'I" respectively.' Leading from the waste air tank I I9 is may be duit I59, a valve I66 being interposed in this condull; to permit or interrupt flow of air therethrough, the valve I60 being actuated by means of a solenoid I6I. I59 leads to a manually operable valve I 62, preferably of the leading by means of a conduit I 64 to the inlet conduit 14 01' the hoist tank "H, and the other outlet I65 leading by means of the conduit I66 to a dust separator I61. The dust separator I61 has an air outlet I66 leading to purpose of muflling the noise of the escaping air, the air passing from the mufiler I69 to the atmosphere.

The blow-oil conduit 15 oi. the hoist tank 1| is connected to a conduit I10 through a valve I1I of the conduit while the third of a conduit I19 to the upper tank 19, a check valve I66 being interposed in the conduit "9 to permit airto flow only outwardly of the upper tank 19 and to prevent reverse fiow.

The present embodiment air compressor I6I for supplying air under pressure to the upper and lower tanks 19 and 8|. The compressor I6I is connected to a storage tank I82 by a suitable conduit as shown. Extending the lower tank 6I interposed a line is a conduit I69 in which are Is; and n5,

position, so that the pressure within the tank 1I may .be relieved by air flow through the conduit I64, the port I65 of the valve I62, the conduit I66, the dust separator tank I61,-the muilier relieved automatically by I12, but this aforesaid appliation and present application.

During operation of theapparatus, air under pressure is delivered directly to the lower tank 8| by means of the conduit I89. Assuming that the material in the of the three-way valve I is turned to compress position, and in this position of the to that in the lower tank 6|. The control lever of the valve I 95 is then moved to "equalize position, whereupon the conduit I92 is shut oil, and communication between the tanks 19 and M is established by means of the conduit I91, the valve I95. and the conduit 260, so as to insure that the pressure within the lower tank 6| is the tank 6|. The control lever of the valve I95 may then be moved to air under a pressure higher. than in the tanks 19 and 6| may be introduced into the uppertank 19 so as to forcethe be of the three-way type similar to the valves I96 of the valve I95 19 is substantially equal material from the tank 19 into the lower tank II. To provide for such higher pressureair, a three-way valve 208 may be interposed in the conduit 200, one port 204, ofthe' valve 208 being connected to a-conduit 205 tapped into the pressure line I89 ahead of the pressure regulator I90 to receive a-higher pressure than exists in the part of the conduit I89 downstream of the regulator. The other ports 208 and 201 of the valve 208 are interp'osed in the conduit 200. Thus with the valve 208 in position to establish communication between the conduit 205 and the part 2001: of the conduit 200, and to cut off communication with the part 200a of the conduit 200, the air under higher pressure in the upperxtank 19 will surge to the lower tank 8|, and will forcibly remove any remaining material from the tank 19.

When all the material has been delivered to the lower tank 8|, the valve 88 is moved to closed position, and the valve 85 is opened, thus feed ing material to the sun 88.

To release the pressure in the upper tank 19, the control lever of the valve I15 is moved to a position indicated by the letter a, in which position the air from the upper tank 19 is permitted to move through the conduit I19, the valve I15, the conduit I52, through the valve I48, and to the waste air tank I49, the-operator being notifled when the maximum pressure in the waste air tank I49 has been reached, either by a signal device, or by the blowing off f the safety valves I50. At this point the operator may move the control lever of the valve I15 to the position indicated by the letter I), so that the remainder of the air under pressure from the upper tank 18 may flow through the conduit I19, the valve I15, the conduit I18, to the dust separator I81, through the mufller I89, and to the atmosphere. After all the air under pressure has beenremoved from the upper tank 19, the control lever of the valve |15 may be returned to its .dead" position; The valve 80 may then be opened, and material may again be hoisted from the hoist tank 1| to the upper tank 19.

The valve 85 is closed when initially charging the apparatus. Movement of the valve 85 may be effected in any suitable way, as by a chain 88| about a'pulley 882, the chain being connected to a lever 885 connected to the plug of the valve. The chain 88| preferably has its operating end positioned adjacent any suitable operating means for the valves 80,- 88, as shown in my aforesaid application but not forming part of the subject matter of the present application.

' The valve 85 may also be closed or interrupting the process temporarily without relieved pressure on thelower feed tank 8|, or at the end of a run prior to a subsequent initial'charging or beginning of operations. In other words, it

is closed before initially charging, or at the end of a days run, or for temporary interruption, and it is. opened when beginning operations, as at .the beginning of a day, or after an interruption as for inspection or adjustment of other equipment.

While the material in the lower feed tank 8| is being ground, the hoist tank 1| will have again been filled, with either new material or with a mixture of new and partly ground material from overage from the screen 98, and this charge will have been hoisted, and all is in readiness to "dump the same into thetank 8| when the lowlevel responsive device in the lower tank 8| indicates sumcient evacuation to receive'the next charge from the upperfeed tank19.

From the foregoing description of the apps.- ratus and the operation thereof, it will be apparent that operation of the apparatus and process are enabled to be continuous, but interruptable whendesired.

Interlock means may be provided, as described in my aforesaid application, so constructed and arranged that certain parts of the apparatus are permitted tooperate only when certain other parts are in a predetermined relation, but these interlock means form no part of the present application.

The valve is interposed in a conduit 888 which has its upper end connected to an outlet tube from the tank 8| and is here shown as having its other end provided with a pair of nipples In the embodiment shown, one of the nipples 881 of the conduit 888 is closed by means of a cap closure 892, while the other nipple 881 has securely clamped thereto one end of the conduit 88. The conduit 88 comprises a heavy-duty flexible tube 898, (see Figures 3 and 4), within which is disposed a heavy-duty rubber hose 894, having its one end securely fastened over one nipple 881 and its other end 895 (see Figure 4) extending into a umon joint 898. The end of the flexible tube 898, adjacent the end 895 of the rubber tube 894, is provided with a coupling device 891 screw-threadedly engaging one end of the union joint, to hold the flexible tube 894 assembled with the union joint. The other end the end 899 is flared outwardly, and receives a metallic funnel-shaped liner 40| preferably formed of cold rolled steel. The bore of the tubular body 400, with the exception of the flared end opening, is uniform in diameter from the end 899 to the other end 402, but at the end 402 the body 400 is formed with an exteriorly threaded reduced extension 408 margining the bore through the tubular body 400. The bore of the tubular body 400 is lined with a material capable of withstanding the abrasive wear produced by the material passing therethrough. 1n the present embodiment this lining is of tungsten carbide, and

in the form of a series of short abutting bushings 404 and a further bushing 405 adjacent the end 402 of the body 400 similar to the bushings 404 but having a tapering bore 408. The opening at that end of the bushing 405 which abuts the adjoining bushing 404 has the same diameter as the opening in this adjoining bushing, while at the opposite end the bore 408 tapers to a reduced diameter as seen at 401. A nut 408 is threaded on the reduced extension 008 of the body 400, suitable packing being interposed between the 1:51: 408 and the adjacent surface of the body counterbore 4| I, the counterbore being of a size to snugly lit a flanged portion 2 formed on a jet nozzle 4|8 (see also Figure '1), the jet nozzle herein being formed of tungsten carbide and havtungsten carbide. .The outer surface 4 4 adjacent the extremity of the nozzle is preferably so formed as to be defined by a cone of straight line generatrix, a generatrix line thereof making an angle of The nut 408 has an opening M0 and a the is provided with an undercut recess 42l receiving the reduced end 422 of a bushing larged end 01' the bushing 423 being exteriorly knurled, as shown at 424 (Figure 4), and being H formed with interior screw-threads for engagement with screw-threads 425iormed on the adjacent'part of the tubular body 488. A lock nut 428 is also threaded onthe screw-threads 428, and holds the bushing 423 against movement.

The other leg 4" of the member 4| 5 is formed witha reduced axially extending threaded. part 421, forming a shoulder 428 with the leg 4| 1. The

the body 429 is also reduced as shown at; 43!, producing a chamber encircling the end 402 and the nut 488 of the tubular body 480, a rubber the opening33 i.

The-bore in the extension 433 communicates with a pressuregauge 435 (see Figure 3), while 428, the enmicrometer wheel the bore inthe extension 434 is connected to a conduit 434a (see Figure 2) which is tapped into the main air pressure conduit I89 ahead of the regulator I90,

barrel.

Referring particularly to Figure 6, the gun 88 comprises an elongated barrel tremity 44l snugly opening 431, and a threaded with the threads 438 448 is then enlarged in outside diameter to provide a portion snugly fitting within the opening 439 pressing a shoulder iformed between the openings 4'38 and 439 of the body 42 a. The bore 443 in the barrel 448 is of uniform diameter throughout, with the exception .01 a

asket against the flaring recess 444 at the extremity ot the barrel 448 adjacent the Jet nozzle 3, the walls of the recess 444 being spaced from the adjacent surtubes 445, providing a barrel diameter. Some oi the bushings 445 may be ofof 7 with the longitudinal axis oi. the bushing 441, and the surface 448 with the tapered end 4 of the jet nozzle 3 to provide an annular air Jet 449 the stream lines of which make a mean angle of about ti with the axis of the nozzle 3.

It will be appreciated that the size of the air jet 449 may be very finely adjusted. To eflect such adjustment, the lock nut 428 is loosened, and the bushing 423 is backed away from the shoulder provided by the leg Then the 420 is rotated in the proper end 4 of the jet nozzle 3 of the tapered and also intermediate markings. A pointer or finger 45L carried by the leg 4l6, cooperates with the-markings on the micrometer its position may be read.

If it is desired that for the position of the parts in which the air jet 449 is such as the letters A, B, C, D, E, and F, to indicate a respective annular line. The lock nut 428 is then drawn up to abut the bushing 423.

To regulate the size'of the air jet 449, the

micrometer wheel 420 is rotated in a direction.

for closing the air Jet 449, so as tubular body 480, causing sep- Any given setting may benoted by the position crease the the rubber lining 459a engaging an of indicia on the plate 456 with respect to the finger 451, and additionally may be noted by the position portion 422 of the bushing 423 with respect to a part of leg 6 of the member 6, such notation being possible by inspection of the letters on the reduced portion 422 through a slot 454 in the leg 6. For instance, the setting A--6 indicates that the air jet 449 is entirely closed; the settin A-- indicates that theair jet is very slightly the setting B6 indicates that the air jet is open still more, and so on. From known. dimensions the jet adjusting means may be readily calibrated so that from any given reading of the indicia on the bushing 423 and on-the micrometer wheel the cross-sectional area of the jet 449 at its outlet will be known.

With the manual valve 436 (Figure 2) in open position, additional booster air, at any desired pressure, may pass through the conduit 434a, to the chamber 43 I, and from there through the air jet 449 in an annular conical stream surrounding the material passing through the bore of the jet nozzle 3, such additional air acting to invelocity of the material moving through the bushings 464 and the bushings 445. The pressure within the chamber 43l may be read on the pressure gauge 435.

The end of the barrel446 opposite to that secured to the body 429, extends through a boss 455 formed on the grinder case 89 Referring particularly to Figures 3 and 8, the grinder case comprises a cylindrical portion 456 and an integral downwardly tapering lower portion 451 terminating in a reduced cylindrical portion 458, the entire interiorof the grinder casev being preferably lined with rubber 459 to prevent the flying material within the grinder case from abradingthe adjacent walls. As indicativ of the small size of the apparatus, it may be stated that in the illustrated embodiment of the apparatus the cylindrical portion 456 is about 12 inches in diameter and has an axial length of about 8 inches. The upper open end of the cylindrical portion 456 is closed by a cover 466, the interior surface of which is also lined with rubber. 45911. The cover 466 formed with a flange 46l fitting withinthe walls of the open end of the cylindrical portion 456,

inwardly extending flange 462 on the portion 456. As shown in Figure 3, the marginal edge of the cover 466 is provided with inwardly extending slots 463, adapted to receive the shanks of bolts 464 swingably mounted on the cylindrical portion 456.

The cover 466 is formed with a-pair of upwardly extending angularly disposed tube portions 416 and 41!, as best seen in Figure 8, the tube portion 416 being closed by a sight glass 412, through which an operator may look into the interior of the grinder case 89. A movable slide 413 is positioned to protect the sight glass 412, the slide 413 being moved to uncover the opening in the tube portion 416 only when it is desired to view the interior of the grinder case 89. The tube portion 41! contains an electric lamp bulb 414, a movable slide 418 being positioned to protect the bulb 414. The interior surfaces of the tube portions 416 and 41!, and the inner surface of the slides 413 and 416, are preferably coated with rubber. Any pressure that may exist within the grinder case 89 may be noted by means of a pressure gauge 411.-

The gun barrel 446 is provided with an elongated longitudinal groove 486 at that portion of the annular lines 452 on the reduced where it passes through the boss 45s, for the .reception oi. the ends of bolts 48! which hold the gun ,barrel 446 against both axial and rotative movement. As seen in Figures 8 and 10, the end of the gun barrel has a reduced extremity 482 and a conical portion 483 spaced inwardly from the extremity, a

- shoulder 484being provided between the reduced,

Herein the anvil 498 also is formed of tungsten comprises a disk extremity 482 and the conical portion 483. A shield plate 485, herein of tungsten carbide, is secured to the barrel 446 at the conical portion 483, in any suitable manner, to restrict movement of the flying particles of ground material. The tungsten carbide bushings 445 extend to the inner extremity of the barrel 446, and an end bushing 486 extends beyond the extremity, and has its end surrounded by a tungsten carbide collar 481 snugly fitting the extending portion of the bushing 486. Thesurlace of the bushing 445 abutting the adjoining bushing 486 is grooved at its left hand end as shown at 488, this groove communicating with a conduit 489 leading to a pressure gauge 496, so that gun muzzle pressure may be noted. Th collar 481 snugly fits within an aperture 491 formed in a ring 492 herein formed of tungsten carbide. An annular housing 493 surrounds and carries the ring 492. The reduced extension 482 of the gun barrel 446 fits within an aperture formed in the annular hous irrg 493.

Diametrically disposed with respect to the boss 455, and extending outwardly from the cylindrical portion 456 of the grinder case 89, is a boss 418, through which extends a tubular body 419, disposed in barrel 446 and formed with an elongated longitudinal groove 494, adapted to receive the ends of bolts 495 to hold the tubular body against both axial and rotative movement. The tubular body 619 has a reduced extremity 496 fitting within an aperture in the annular housing 493, the ring 492 also being apertured at this point to receive a. tungsten carbide collar 491. An anvil 498 is slidably disposed in the collar 491.

carbide. The anvil 498 need be of a diameter only about one and one-half to two times the diameter of the opening in the tungsten carbide bushings lining the gun barrel 446. One end of the anvil 498 i directed toward th gunbarrel 498 is firmly gripped by opening, and is spaced a slight distance from the muzzle of the gun barrel, one-half inch to one inch having been found satisfactory under usual circumstances. The other endof the anvil an adjusting screw 499 interengaging with screw-threads formed on the interior of the body 419 and having a diametrical slot 566 in its outwardly directed end so that a screw-driver may be inserted in the opening of the tubular body 419 and engage the slot 566 a shield plate to effect adjustment of the anvil 498 toward or away from the muzzle of the gun barrel 446. The end of-the tubular body 419 adjacent the annular housing 493 is also preferably provided with 56l to restrict movement of the flying particles of ground material and herein formed of tungsten carbide.

Excellent results have been had with an anvil of thefpencil type, the diameter of the anvil not greatly exceeding the diameter of the bore of the bushing 486, in the present instance the bore of the bushing 486 (as well as that of the bushings 445) being about .180 of an inch in diameter and the anvil being about of an inch in diameter. The end of. the anvil, in the 446 within the grinder case 38 axial alinement with the gun 7 present embodiment, is positioned about three-: quarters of an inch from the muzzle of the gun barrel, although this distance may be varied, as will be obvious, by adjustment of the screw 499, and in any event preferably the anvil is close It has been found in practice that an anvil witha perfectly flat surface directed toward the particles expelled by the gun barrel, quite rapidly has formed therein a crater 502 of conoidal form having a small central projection, as best seen in Figure 10. It will be noted that of the crater 502 is defined by the cross-sectional outline of the anvil 498. Once this crater is formed, the wear on the anvil is extremely slight, because the material is ground by impact of particles against particles in the crater. In practice, upwards of a hundred tons of material have been ground without showing any appreciable wear on the anvil. Furthermore, any wear on the anvil is even, that is, the crater 502 remains stantially uniform and very slow reduction in length of the anvil portion 498. Such is not the case if the cross-sectional area of the anvil is considerably larger than that of the bore of the gun muzzle. In that case the crater is of commore rapidly, and as it wears, the form of the crater varies, and the wear does not result inuni-form reduction in length of the anvil.

It may be here stated that the bushings 404 (Figure 6) lining the gun breach are preferably of larger bore'than those in the gun barrel 440, a diameter of .250of an inch having opposite sides of the ring 492 and annular housing 493, as best seen in Figures 9 and 10. Each rod 503 is provided with a screwg for receiving a screw-threaded the rim asezus grinder case 89, any kinetic energy remaining after the material has been ground by impact in the crater 502 being largely absorbed by the rod SID. The rods 5") are borne through packings in thecylindrical portion 456 01' the grinder the grinder case 89.

The ring 492 and annular housing 493 have additional diametrically opposed openings, disposed substantially at right angles to the openmgs receiving the gun barrel 440 and the tubular body 419, and threaded to receive the threaded Immediately rearward of the disk reduced end H3 is formed with an annular groove SIG. Radially extending apertures Ell, formed in each body 5, communicate with the space provided by the interior of the ring 492, through the slight space between the margin of the disk SIS and the adjacent surface of the opening in the ring 492 and through the annular groove 5H5, and extend into communication with a bore 5l8 formed in each tubular body 5l4. The outer extremity of each bore H9 is closed by a plug 5| 9, and one of these plugs may be apertured to provide communication with a pressure gauge 520, so that the pressure within and threaded on the ends'522, to clamp the rods 52| in position. and to assist in supporting the tubular bodies 5.

With the exception of parts herein of tungsten carbide, all 01' the parts within the grinder case rubber applied in any suitable way.

In some and an annular housing 499a, v 492 and annular housing 493 hereinbefore described. As before, the ring 492a and the annular housing 493a are formed with apertures disposed approximately apart, but in this case none of the apertures is 81 already the interior of which is ment with the guns aperture "I to meet hereinbefore lined with bushings la herein of tungsten carbide. and each barrel (la is formed with a reduced end 482a fitting within a respective opening formed in the annular housing la, the innermost bushing 8a extending outwardly of the gun barrel a and being surrounded by a tungsten carbide collar 48111.

In the construction shown in Figure 11, each gun projects material at high velocity toward the center of the ring 492a, the material thus projected, instead of striking on an anvil as before described, now strikes a counter-stream of material from an oppositely disposed gun, and also strikes a lateral stream of material from a transversely disposed gun. However, two oppositely disposed guns may be omitted, thus providing only one air of oppositely disposed gun's, each projecting a stream of material against a counter-stream projectedby the opposite gun.

Referring particularly to Figure 12, there is shown a pair of oppositely disposed guns Mb, similar to the guns 8! hereinbefore described, the guns 88b comprising gun barrels lib having reduced ends "2b disposed within apertures in supports I. As before, around the extending ends of the innermost bushings "6b are disposed collars 481b herein of tungsten carbide. However, in this embodiment an anvil 525 of tungsten carbide is positioned intermediate the guns lib, opposite surfaces toward respective gun muzzles. The anvil 525 is shown as having its ends formed with craters such as those formed after the anvil has been in use a short time. The anvil 525 may be supported in any suitable manner in alinement with the gun ends, as for instance by means of a support 521.

Referring particularly to Figure 13,- oppositely disposed guns "0 are provided, each gun being similar in construction to the gun 80 hereinbefore described, and comprising a gun barrel 0c having a reduced end "2c fitting into an opening in a support 528, the extending portion of the innermost bushing 4880, as before, being surrounded by a collar "1c herein of tungsten carbide. In this particular embodiment an anvil 52! of tungsten carbide is disposed in axial aline- 88c, and is spaced from the outlet of each gun, and is provided in its ends with recesses 530 each tapering to a reduced central aperture "I. The recesses 530 serve the function of a funnel, directing the stream of material from each gun toward the reduced the counter-stream from the opposite gun.

Figure 1i shows what 1 term a two-stage gun, Figure 15 shows a three-stage gun, and Figures 16 through 18 show a type of gun of more than three stages, although guns of more than three stages may be of the type shown in Figures 14 and 15. By the provision of a plurality of stages 1'. mean the provision of more than one booster jet, such as 9, Figure 'l, suitably placed .to increase the velocity of the stream of material in the gun barrel means, and for other purposes. The purposes and results of this method of propelling the material through the gun barrel will appear hereinafter.

Referring particularly to Figure 14 the construction therein shown provides two successive accelerating jets. The construction comprises a breach 81d, similar to the breach 81 described, having a generally U- shaped member llld forming legs Mid and "111 connected by an integral bight llld. A microm- 528 being directed eter wheel purpose of adjusting the jet opening 9d, the

jet opening receiving a supply of booster air through an opening in a lateral extension "id. An oppositely disposed lateral extension 433d has an opening 1eading to a pressure gauge (not shown). The Jet 8d discharges into a gun barrel 0d. The bore of the jet nozzle of the Jet 812 (corresponding to the jet nozzle bushing H3) is preferably slightly smaller than the bore of the gun lid, although it may be equal to but preferably not greater than the bore of the bushings corresponding to the bushings 5 and 1.

The gun barrel 0d, instead of extending to the grinder case, extends to another gun breach Ble, in which in this instance the member "be is generally O-shaped, with legs is and 1e having their corresponding ends joined by integral bights llle. The breach l'le includes an air jet is provided by a jet nozzle bushing and a cooperating bushing analogous to the jet nozzle bushing H3 and cooperating bushing "1 of Figure 6. A, micrometer wheel 420a provides for adjustment of the airjet 90. A lateral extension lfle has a bore providing for a supply of additional booster air oppositely disposed lateral extension 433a has a bore communicating with a pressure gauge (not shown). A gun barrel he extends from the breach Ole and leads to the grinder case, similar to the grinder case 89, the gun barrel lie being similar in construction to the gun barrel us hereinbefore described. The jet nozzle of the Jet 9e (corresponding to the bushing H3) is preferably of a design no smaller than the preceding bushings, while the subsequent bushings corresponding in function to the bushings I and 441 of Figure 6, preferably are the same bore size as that of the preceding jet nozzle, or may be slightly larger, such as 5 to 15% larger than the preceding diameter, depending on the absolute size of the gun bore concerned, although they may be the same as that nozzle.

Readings of the micrometer wheels 2011 and 420s may be taken with reference to pointers 45 i d and la respectively, and the adjustment of the jets 9d and 9e additionally determined as already fully explained in connection withthe breach 81 'of Figures 4 through 7. The booster air admitted through the bores in the extensions "4d and 134a may be under the same pressure, as for instance 500 pounds per square inch. However, the pressures may be unequal, the pressure of the air through the opening of the extension l3le being, for example, greater than the pressure of the air in the extension Id. The breach .8Ie is made of 0-shape to provide for pressures of the order of 1000 pounds per square inch.

If desired, another or more breaches similar to the breach 81c shown in Figure 14 may be added in series, thus providing for booster air at a plurality of predetermined places along the gun barrel means. Figure 15 shows an arrangement providing for three stages of booster air. This arrangement uses three gun breaches 81f, 81g, and 81h, the breach to the breach s1 and the breaches 81g and 81h being each similar to the breach 81s of Figure 14, these breaches providing booster jets 9f, 9g, and 9h. The breaches 811, 81g, and 81h, are connected in series, to, constitute part of the gun barrel 0}, 440g, in.

In general, with respect to guns of the type llustrated in Figures 14 and 15, the jet nozzle of the preceding jet ms is provided, as before, for the to the air, jet 9e. An

81;! being similar" bushings in the stages subsequ to the first bores I. it may be necessary to use small ringstage are preferably-o! a design no smaller than like bushings I. v the preceding bushings, and the subsequent bush- In the construction shown in- Figures 16 'ings corresponding in functioning to the bushings through 18, it will be seen that booster air may us and 1 01' Figure 6 are the same bore size as] en the b 540 and t av e the ope in 535 that of the preceding jet, or may be slightly n h ody- 2, p ss through the radial op larger, such as 5 to 15 percent larger than the lugs ill in the barrel I36, and the openi s 550 preceding diameter, depending on the absolute n t in s 545, and emerge throu h th air size 01' the gun bore concerned, although they Jets!" as streams oi air surrounding the matemay be the same as that of the preceding Jet. 10 ria Pas in through the bushings lining the 8 m Figures 16 through 18 show another gun conbarrel 536. In a multi-stage barrel section such struction also provi, g for jets of booster airf as illustrated in Figure 16, the bore is pref ra at a plurality oi predetermined places along the the same throughout.

length of the gun. Referring particularly to f desired. a sun construction such as shown Figure 16, the gun therein shown comprises a in Figures 16 through 18 may be used with any generally cylindrical body 532 having an en one of the other types of guns preceding it. A larged internally threaded head 533 at one end gun construction of this type is shown in Figure and an externallythreaded portion 534 at the n w i a breath (which m y be Similar tudinal bore 535. Extending through the bore 20 barrel port on M (whi h may be similar to the diameter t bore 5 providing an breach portion 811 (which may be similar to the nular space 53'! extending about the gun barrel breach 111 n nne ted to a 81in barrel 5". Adjacent the end 534, the bore 535 is formed portion "to 01 .a multi-stage gun 532a constructwith an annular recess communicating with diaed and arrenfled Similarlyto he m-s ge un imetrically extending bores 539 and m, the bore shown in Figures 16 through 18, so that the 53! communicating with a pressure gaug (not 4 bushings therein provide a succession of fixed or predetermined spaced intervals along the length so lets through a single inl t pipe 4 a. th re bein of the gun body 538, the gun body is f r ed also a pipe 539a connectable to a pressure gauge with radially extending apertures I. Th gun (not shown) on which the pressure within the body! is held in position by meansof nuts 54: chamber corresponding to the chamber 538 of and 543 screw-threadedly engaging the respecure 16 may be noted. It will-be understood tive ends 533 and 634 oi. the body 532: that the gun 532a has a barrel portion 63Gb (the Th opening through th gun barrel 539 is terminus of which is the muzzle of the sun) of lined with bushings herein formed of tungsten desired and suitable l th- It will be evicarbide. the bushings m in those portions 01 u t a the s n nstruction shown in Figure the body 682 being generally similar to the bush- 40 stages preceded by a desired number 01' adjustaexteriorsurtace of which is conical. a straight obtained h five fixed stages and, as shown, two

ing. The opposite end 541 of each bushing 54s is largest 1111101111 01 ramaterialformed with an inwardly tapering recess 543 Another Bun construction is shown in Figure adapted to cooperate with the nozzle m of an so in which a 811.11 me, similar to etiother t the r the pbmon 5" abuts a nection 10! directly .to a material feed conduit shoulderv on the adjacent bush ngleaving an air which may cm'respond to the material feed Jet passage m. The generatrix oi the'conical 55 Conduit at is, the conduit 10: may lead surface of the recess 5 preferably forms a 7' directly the feed tank 3| the E m- File,

jet passage 5 has a mean angle or 00 or an end bushing "do of the barrel 536a (corre- The .end s41 01' the bushing m is formed with the end bushing M the radially extending apertures I50, providing combarrel Figure 16) The type gun 'munication between the radially extending bores m Figure 20 may be used after the require" "I and the jet passage 9. Referring to ments of a specific application have been deter- Figures 16 and 17, the'extreme left end bushing a s o d with a j nozzle 6 y at its rial. the hardness and resistance to fracture, the

right hand end, the other end being plain, to

t an a jacent bushing I, and the bushing .t rm] me at the extreme right handend of the body e number stages erlyaline the bushings I with respective radial 7;; portion 536d maybe ny suita K h p to 9 for any give;h application will depend on the separating device 9|.

' .180 of an inch. In this type of gun such range of adjustment as may be needed is obtained by adjusting the air input pressure. as well as the solids feed pressure, in order to control to a certain extent the rate, size, and character, of the output.

Figure 21 illustrates another type of gun arrangement, in which two guns I and I00 are so related that the streams from the muzzles thereof impinge each other at some angle less than 180, in the illustrated instance 90. The muzzles of the guns 105 and I08 may be disposed through an annular member 101 corresponding to the annular member 493. The annular member 101, besides having apertures to receive the guns I and I00, may be provided with an aperture to receive an anvil carrying member I08 similar to the member 410, the axis of the member I00 bisecting the angle between the streams from the guns I00 and I00, and an anvil I00 carried by the member I00 being disposed approximately at the place of impingement of the streams.

The material ground in the grinder case 09 (see Figure 8) gravitates down the rubber-lined sides 451 to the reduced outlet 408 and thence through the conduit connection 00 to the first separating device 91, this connection including a fitting '552 (see Figure 3) to which is attached one end of a flexible hose 553 the opposite end of which is attached to an inlet pipe '554 of the first As shown in Figure 1, the first separating device 9i has another inlet pipe 555 directly below the inlet pipe 554, but the inlet pipe 555 in this instance is closed by a cap 556. If desired, the inlet pipe!!! may lead to another grinder case, the tank Si in such instance serving both grinder casings, or the pipe 555 may be used as an inspection opening.

Returning now to a consideration of the methods by which the material is ground, I have used with excellent results a gun having a bore of .180 of an inch, provided with a single accelerating jet, and having a length from the accelerating jet to the muzzle of the gun of approximately 54 inches. It will be noted that in this instance the area of the bore is approximately .025 of a square inch, and since the length, is 54 inches, the ratio of inch length to'square inch area of bore is approximately 2100. However, also I have used with excellent results a gun having the same bore area and a barrel length of 44 inches, the ratio of inch length to square inch bore area being in this instance approximately 1'700. A further example is a gun of the same bore area but having a length of 1 inches, in which instance the aforesaid ratio is approximately 390. 'These examples are given as illustrative, and it is to be understood that my invention is not limited to these particular dimensions or ratios, and in fact at least part of my purposes may be accomplished when the aforesaid ratio is as low as approximately 200.

In considering the action of a single stagegun, that is, a gun having a single accelerating jet, constructed in accordance with my invention, the mixed stream of material and air which enters the bore of the bushing 441 (Figures 6 and 7) maybe conceived theoretically as a core which is surrounded by the internal surface of an annular stream provided by the jet 440. This annular stream at the moment it issues from the jet aperture is moving at a much greater velocity than the core, and acts to impart its velocity to the immediately adjacent outer suface elements of the core, and these in turn act to impart their velocity to the elements of the core radially inward of the core. Obviously the center of the core will not acquire the velocity of the annular stream instantaneously, or for an appreciable period or distance, and the acceleration of the core is rendered more diflicult because the solid material in the core accelerates less rapidly than the air. Under these conditions, it is evident that acceleration of the core must take place, at least initially, largely by application of force at the outer surface of the core. However, if the diameter of the core is increased, thearea and content of the core increases as the square of the radius, whereas the circumference increases only as the first power of the radius. Thus for a gun having a bore twice as large as another, the theoretical surface at which accelerating force is initially applied is approximately twice as large, whereas the core which is being accelerated has an area and a mass approximately four times as large. As far as the foregoing considerations are concerned, obviously it is highly desirable that the core be relatively small, or in other words, that the bore of the gun be relatively small, particularly if the gun is a single stage gun. However, the jet must have a substantial kinetic energy, which presumably can be secured at given pressure adjustment to a suitable jet area, or at a given jet area by adjustment to a suitable pressure of the booster air, or by some combination of the two. It seems that increase of the jet area would involve greaterpenetration of the annular jet into the core, but however that may be, I have found that within limits which will be referred to, an increase of jet area is beneficial, and seems to involve a more positive impelling action of the jet on the core than is involved in considering the jet as impelling the core merely by the theoretical inner annular surface of the jet along the theoretical outer surface of the core. Nevertheless, I have found that there is an optimum relation between the area of the jet and the area of the gun bore.

In a gun of more than one stage the bore of the gun may be made larger than for a gun of a lesser number of stages, but I have not found the use of relatively larger bores necessary, because with a plurality of stages the velocity of the material, the fineness of the product, the production, and the efficiency, may be still further increased even with a gun bore no larger than that of a.single stage gun. Obviously this is exceedingly important, for example in respect of the weight and expense of the equipment, particularly the cost of the parts made of tungsten carbide or other suitable wear-resisting material. However, before-discussing plural stage guns further, there maybe considered results I have obtained on the single stage guns.

For'example, I have obtained the following results using a gun having a bore diameter of- .180 of an inch and a length of 54 inches from the jet 449 to the muzzle. of the gun barrel 440, the stream being directed against an anvil such as the anvil .490. The positive pressure behind the stream, as furnished by the air underpressure in the feed 8|, was approximately 500 to 550 pounds per square inch, and air was fed to the jet 449, through the connection 434, also at a pressure of approximately 500 to 550 pounds per square inch. The solid material fed from the feed tank 8| was zircon (ZrSiO4) of -60 mesh comprising substantially no particles proximately l2,250 cubic feet. The ratio of the volume of solid material to the volume of themixture of compressed air and sclid material comprising the stream projected from .the gun muzzle, was 2.15 percent. The material was passed through the gun once, with the results shown in the following table, Number I, in which for each minus mesh size produced there is givenin column A the number of pounds thereof prodused per hour, and in column B the cubic feet of free air which was compressed and used per ton produced:

Table Number I Mes]: A

In connection with these results it may be observed that zircon is not only'very hard and abrasiv but also very tough, and these characteristics render its impact resistance high and make it diillcult to grind. Furthermore, it is well known that it is extremely difilcult to further grind or pulverize materials which are already relatively line, .due to the fact that the impact energy decreases while the resistance to fracturing remains approximately constant. By way of example, it is more difllcult to break down by impact to half its volume a material particle in'the range of 200 mesh and flnerthan it is in the coarser ranges.

It seems that in a-single stage gun the optimum ratio between the cross-sectional area of the accelerating jet, and the cross-sectional area of the gun bore, is approximately 40 to approximately percent. In general, the net result of putting more than a certain limited amount of energy into the must one point, is that entrainment of solids is seriously reduced, that is, the feed of solids is decelerated, and the consumption of air per ton of feed is too greatly increased to be economical. In fact, with too high an energy input at a single point of the gun, the solids feed may even be choked oil.

However, I have found that this difllculty may be overcome by using successive Jets, at points spaced longitudinally of. the gun, each jet having a desired cross-sectional area and being supplied at a desired pressure, so that the stream is permitted to increase in velocity before a second accelerating jet acts on the stream to further increase itsvelocity, and so on. With such a gun the solids feed to the gun is not choked ofl nor materially reduced, even with high gas pressures, and can be regulated to a desired richness of solids-gas mixture merely by regulating the pressure on the multiple Jets and the pressure on the feed tank 8|. Moreover, it is possible to get results quite out of "proportion to increase in pressure, and in fact, the use of high pressure is made possible, and the advantages thereof are realized, without resulting in choking on or seriously reducing the solids feed. Withsuch a gun the maximum gas pressure and velocity appear to be limited only by construction problems. Furthermore, great gun barrel length is made possible without introducing offsetting disad-- vantages, thereby overcoming excess "slip of the solids in the gas stream.

I have further found that in a plural stage gun, even if the sum of the cross-sectional areas of the successive jets be no more or not'substantially more than the cross-sectional area of the optimum size jet for a single stage gun, and .even if the bore of the plural stage gun be no different than that of a single stage gun, yet the results producedare far superior. 'Furthermore, I have found that in a plural stage gun the ratio of the sum of the cross-sectional areas of the jets to the cross-sectional area of the gun bore may be inenergy state existing at that point.

The gist of a principle underlying my invention creased much beyond the optimum ratio for .a single stage gun, in fact the ratio may approach and even exceed 100 percent, without substantial impediment of the solids feed. The respective jet pressures need not be the same as the positive pressure on the stream at the breach of the gun, but may be either higher or lower, depending upon the Jet opening which happens to work best at-a particular point, the important thing being (a) the total energy supplied at that point, and (b) remaining within limits of the maximum desirable jet openingarea for asingle stage which in turn depends onthe velocity and particle is the applying of energy in controlled stages dependent upon various limitations, particularly the particle energy state existing at a particular point in the gun barrel, and that again is the result of the velocity, size, shape, and specific gravity, of the material particles, existing at that particular point. If it is endeavored to boost too much either by wayof Jet area or by way of pressure, the result may be instead to decelerate and interfere.

An example of the functioning of a two stage gun-is afforded by results obtained on a gun of the type shown in Figure 14 which had a bore diameter of .180 of an inch and in which the gun barrel portion be had a length from the jet 9e to the muzzle of the portion lie of approximately 34 inches.- The length of the gun portion ad from the jet 9d to the jet Me was approximate- I approximately 16% of the area of the gun bore,-.

1y 20 inches. The stream from the muzzle of the gun was directed against an anvil such as the anvil 488. In one of the runs the jets had a combined-area of approximately 56 percent of the gun bore, the jet 9d being set so that its area was and the jet 9e being set so that its area was approximately 40% of the area of the gun bore. The; air supplied to the gun from the tank ill, and the air supplied to the jets 9d and 9e, was at a upressure of approximately 500 to 540 pounds per square inch. The solid material fed to the gun was the same kind of material as in the case of the single stage gun hereinbefore referred to. and there resulted a feed of approximately 1865 poundsper hour. The quantity of free aircompressed and used per ton of solids feed was approximately 7517 cubic feet. The ratio of the volume of solid material to the compressed air and solids mixture volume, was approximately 3.54%. The material was passed through the gun once, with the results shown in the followv I creams.

.lng table, Number II, in which the columns have thesam'e meaning as in Table Number I:

Table Number ,II

Mesb A B 947 14.760 -g l i m 18,510 a ass 21.040 m 819' -22. m i n 635 .An example of the functioning of a three stage gunis ailorded by results obtained on a ,gun'cf the type shown in Figurel5, having a bore of .180 of an inch. The gun barrel portion on was approximate1yj34 inches from the jet M to the muzzle of the gun, the gun barrel portion lo was approximately 10 inchesirom the jet to to the jetllsh, and the gun barrel portion 0! was approximately 10 inches from the jet 9! to the jet la. The stream from the muzzle of the gun was directed against an anvil such as the anvil l. in oneot the runs the combined area; of the jets was approximately 78 percent of the gun bore area, the Jets 9!, to, and 8h, being ,so set that their areas wereapproximately percent, 24 percent, and 34 percent, respectively, of the area of the gun bore. The air supplied to the gun'i'rom the tank 8|, and the air supplied to the Jets 0/, 9g, and 9h, was at a pressure of approximately 500 to 550 pounds per square inch. The solid material fed to the gun was the same lrind of material as in the case of the single stage gun test hereinbetore referred to, and there resulted a feed of approximately 2280 pounds per hard materials have been rapid wear and damage to the grinding means, and the introduction into the product 0! added material from grinding undesirable in most instances.

means. Such added material from the grinding means is hereinafter referred to as additions. The introduction or additions into the product is An example is zircon, ground by a prior art method, which had a bluish gray color, a relatively low electrical resistivity, and a lowered fusing point, due to metallic iron inclusion. These defects render the zircon unsuitable for use for example as a refractory electrical insulating material particularly at elevated temperatures. It is sometimes attempted to remove the additions or other impurities by treatment with chemicals, but this necessitates subsequent removal or the chemicals, and also, is not necessarily successful, and in fact, may leave not only the previous impurities but also some of the chemicals used in the 7. to 7 (Mohs' scale), has been hereinbefore used as an example of the grinding of hard materials, it is of course to be understood that mate- -rials or substantially any hardness may be hour. The quantity of the air compressed and a used per ton of solids feed was approximately 5530 cubic feet. The ratioof the volume of solid material to the compressed air and solids mixture volume was approximately 4.76 percent. The material was passed through the gun once, with the results shown in the following table, Number III, in which the columns have the same meaning as in Table Number I:

The power consumption to produce the foregoing results of course is that required to compress the air, and by way of example, in the case of the two-stage gun, the power consumption was approximatelyas follows:

KWH per ton oi -200 mesh 82 KWH per ton of -300 mesh 85 KWH per ton of 325 mesh 98 KWH per ton of -400 mesh It is of course evident'lrom a comparison of Table Number III with Table Number II that the air consumption and power consumption per ton of each size of product was materially less in the case of the three-stage gun than in the case of the two-stage gun. Furthermore, as the numcontaminate the product, but, as set forth'in nu! her of stages is increased, in general the hourly production rate is materially increased, even though the gun is neither longer nor of greater bore.

ground to great fineness without contamination.

This is due in part to the fact that the gun is so constructed and arranged that it may be and is .lined with tungsten carbide or other suitable wear-resisting material, in all portions where material wear might occur, and isdue in part tothe provision and continuance by the accelerating jet or Jets of a protecting sheath of air between the surface of the gun bore and the material-carrying stream. However, the construction and arrangement oi the anvil, and mode of cooperation of the anvil andthe projected stream of material, whereby there is substantially no wear ofthe anvil, also is a material factor in preventing contamination.

My invention is particularly useful in the grinding of the harder materials, of hardness 4 or more (Mohs scale), and will readily and efilciently grind such materials for example to '200 mesh with less than ,5 additions, to -325 mesh with less than 9 6% additions,.and to --'400 mesh with less than 35 additions. In fact, my apparatus will grind readily and efliciently with substantially no additions whatever. For example, with apparatus embodying my invention I have ground 100 tons of zircon (about 12 cubic feet to the ton) with loss from the grinding apparatus of ie of one cubic inch, which represents additions carried into the material from the.

grinding apparatus of approximately one part in one hundred million, and even of this-minute.

amount, part is removed with impurities previously present in the material. In fact, not only are there substantially no additions that would aforesaidapplication, the material may beso ground that the greatest traction of the ground product contains less impurities than the raw material, or substantially no impurities.

My apparatus is particularly well adapted for use where different degrees of impact are, desired, particularly because of the great flexibility of adjustment, whereby substantially, any desired 

